Exhaust system including ionization assembly

ABSTRACT

An exhaust system includes an electrically conductive shell defining an exhaust pathway. The shell includes a tapered portion that tapers inward toward a longitudinal axis of the shell to define a narrowing region of the exhaust pathway. The exhaust system further includes an ionization assembly and an electrical subsystem that applies an electrical potential difference between the shell and at least a portion of the ionization assembly located within the exhaust pathway. The ionization assembly includes a support arm located within the exhaust pathway that extends into the narrowing region of the exhaust pathway. The ionization assembly further includes a plurality of electrically conductive discs mounted on and supported by the support arm. The ionization assembly is electrically insulated from the shell by an electrically insulating support structure.

BACKGROUND

Products of combustion in the form of exhaust gases may be directedthrough an exhaust system where the exhaust gases may be treated beforebeing discharged to the environment or other suitable location. Avariety of exhaust system configurations, and chemical and/or physicalprocessing techniques may be used to remove and sequester products ofcombustion from the exhaust gases before discharging the remainingcomponents.

SUMMARY

According to an aspect of the present disclosure, an exhaust systemionizes exhaust gases to remove products of combustion from an exhauststream. The exhaust system includes an electrically conductive shelldefining an exhaust pathway. The shell has a tapered portion that tapersinward to define a narrowing region of the exhaust pathway. The exhaustsystem further includes an ionization assembly and an electricalsubsystem that applies an electrical potential difference between theshell and at least a portion of the ionization assembly located withinthe exhaust pathway.

The ionization assembly includes a support arm located within theexhaust pathway that extends into and along the narrowing region of theexhaust pathway. The ionization assembly further includes a plurality ofelectrically conductive discs mounted on and supported by the supportarm. At least some of the discs are located within the narrowing regionof the exhaust pathway, and are spaced apart from each other along alongitudinal axis of the exhaust pathway. The discs decrease in sizerelative to each other along the longitudinal axis with tapering of theshell. Components of the ionization assembly, such as the support armand the discs are electrically insulated from the shell by anelectrically insulating support structure.

A voltage source of the electrical subsystem includes a high electricalpotential terminal in electrical communication with the shell, and a lowelectrical potential terminal in electrical communication with the discsto apply an electrical potential difference between the shell and thediscs. Particles within exhaust gases traveling along the exhaustpathway are ionized and become negatively charged by the low electricalpotential applied to the discs. These negatively charged particles areattracted by the high electrical potential of the shell. A filterelement located along an inner surface of the tapered portion of theshell that surrounds the narrowing region of the exhaust pathwaycaptures larger ionized particles, such as particulate matter or otherproducts of combustion contained in the exhaust gases.

This Summary describes aspects of the present disclosure in a simplifiedform. This Summary is not intended to identify key features or essentialfeatures of claimed subject matter, nor is this Summary intended tolimit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts an internal view of an example exhaust system.

FIG. 2 depicts an example external view of the exhaust system of FIG. 1.

FIG. 3 depicts another example external view of the exhaust system ofFIG. 1 with optional components omitted.

FIG. 4 depicts an exploded view of the example exhaust system.

FIG. 5 depicts the example insulating support structure of FIG. 1 infurther detail.

FIG. 6 depicts an example of an overlapping region between shellcomponents of the exhaust system of FIG. 1.

FIGS. 7 and 8 depict additional aspects of the example ionizationassembly of FIG. 1 as exploded view and assembled views, respectively.

FIGS. 9 and 10 depict a non-limiting example of an electricallyconductive disc in further detail.

DETAILED DESCRIPTION

FIG. 1 depicts an internal view of an example exhaust system 100 thationizes exhaust gases to remove products of combustion and incompletecombustion from an exhaust stream. Exhaust system 100 includes anelectrically conductive shell 110 defining an exhaust pathway 112. Shell110 forms a generally tubular structure to convey exhaust gases alongexhaust pathway 112. In this example, shell 110 may have a circularshape when viewed in section along a longitudinal axis 114 of shell 110.In other examples, shell 110 may have a non-circular shape when viewedin section, such as a non-circular oval shape, polygonal shape, or othersuitable shape. Example section views of shell 110 are depicted in FIGS.4-6.

Shell 110 includes a tapered portion 128 that tapers inward towardlongitudinal axis 114 in a first direction 116 along longitudinal axis114. Tapered portion 128 defines a narrowing region 118 of exhaustpathway 112 that narrows in the first direction 116 along longitudinalaxis 114. In this example, first direction 116 corresponds to a flowdirection of exhaust gases along exhaust pathway 112 in whichlongitudinal axis 114 of shell 110 is oriented parallel to theX-coordinate axis.

Exhaust system 100 includes an ionization assembly 140. Ionizationassembly 140 includes a support arm 142 located within exhaust pathway112. Support arm 142 extends into and along at least a portion ofnarrowing region 118 of exhaust pathway 112. Support arm 142 may besupported relative to shell 110 and electrically insulated from shell110 by an electrically insulating support structure 144. Supportstructure 144 serves as an electrical insulator that electricallyinsulates discs 146 and/or support arm 142 from shell 110. In thisexample, support arm 142 projects from support structure 144 in thefirst direction 116 along longitudinal axis 114 and is collinear withthe longitudinal axis. In other examples, support arm 142 may beparallel to and offset from the longitudinal axis. Also in otherexamples, support arm 142 may extend in an opposite or counter directionfrom the direct depicted in FIG. 1 in which the support arm projectsupstream from an electrically insulating support structure.

FIG. 1 depicts support structure 144 being located within the exhaustpathway. Support structure 144 may be secured to the shell at one ormore points via one or more mounting surfaces of the support structure.In this example, support structure 144 has three mounting surfaces forsecuring the support structure to shell 110 at three points radiallyspaced apart from each other about longitudinal axis 114. Two of thesepoints are depicted in FIG. 1 at 180 and 182. Support structure 144 isdepicted in further detail with reference to FIGS. 4, 5, 7, and 8.

Ionization assembly 140 includes a plurality of electrically conductivediscs 146 mounted on and supported by support arm 142. In this example,ionization assembly 140 includes six discs, indicated individually byreference numerals 150-160. In other examples, an ionization assemblymay include a single electrically conductive disc or 2, 3, 4, 5, 7, 8,9, 10 or more electrically conductive discs. At least some or all ofdiscs 146 may be located within narrowing region 118 of exhaust pathway112. In other embodiments, narrowing region 118 may instead be anon-narrowing region, and expanding region, cylindrical, etc.

Discs 146 are spaced apart from each other along longitudinal axis 114and along the support arm 142. In at least some examples, some or all ofdiscs 146 may have different sizes and/or shapes relative to some or allof the other discs. In this example, discs 146 have a circular shapewhen viewed along longitudinal axis 114, and decrease in size (e.g., indiameter or width as measured in a plane that is orthogonal tolongitudinal axis 114) relative to each other in first direction 116along longitudinal axis 114 and along support arm 142. For example, disc150 is larger than disc 152, disc 152 is larger than disc 154, disc 154is larger than disc 156, disc 156 is larger than disc 158, and disc 158is larger than 160. In other examples, at least some or all of discs 146may have the same size and/or shape relative to each other. Also inother examples, at least some or all of discs 146 may have anon-circular shape when viewed along longitudinal axis 114, including anon-circular oval shape, polygonal shape, or other suitable shape.

Exhaust system 100 includes an electrical subsystem 170. Electricalsubsystem 170 includes a voltage source 172 having a high (e.g.,positive charge relative to a ground reference) electrical potentialterminal 174 in electrical communication with shell 110, and a low(e.g., negative charge relative to a ground reference) electricalpotential terminal 176 in electrical communication with discs 146. Inthis example, a high electrical potential is applied to shell 110 byvoltage source 172 via a first electrical pathway 178 that is incommunication with high electrical potential terminal 174, and a lowelectrical potential is applied by voltage source 172 via a secondelectrical pathway 179 to discs 146 via low electrical potentialterminal 176 to create an electrical potential difference between shell110 and discs 146. In some examples, support arm 142 may take the formof an electrically conductive support arm that is also in electricalcommunication with low electrical potential terminal 176 (e.g., viaelectrical pathway 179) and with each of discs 146, so that a lowelectrical potential is applied to both support arm 142 and discs 146.As an example, support arm 142, as an electrically conductive supportarm, may form part of electrical pathway 179 that electrically couplesdiscs 146 to low electrical potential terminal 176.

Voltage source 172 is depicted schematically in FIG. 1, and may takeother suitable forms and may be positioned at other suitable locationsrelative to shell 110. Voltage source 172 may be implemented as anelectric battery, an electric motor, or other suitable device or systemthat provides an electrical potential difference that may be appliedbetween shell 110 and discs 146. In some examples, one or both ofelectrical pathways 178, 179 may include one or more intermediateswitches that enable one or both of the electrical pathways 178, 179 tobe opened to disconnect voltage source 172 from exhaust systemcomponents, and thereby remove the electrical potential difference frombetween shell 110 and discs 146.

During operation of exhaust system 100, exhaust gases traveling alongexhaust pathway 112 in the first direction 116 enter shell 110 via inletportion 120. Particles within the exhaust gases are ionized and becomenegatively charged by the low electrical potential applied to discs 146.These negatively charged particles are attracted by the high electricalpotential of shell 110. Narrowing region 118 may further compressexhaust gases traveling along exhaust path 112 within the vicinity ofdiscs 146 to further improve ionization of exhaust gases at surfaces ofthe discs and/or support arm 142, which in turn increases the removal ofexhaust components from the exhaust gases.

In at least some examples, exhaust system 100 may include a filterelement 190 located along an inner surface of tapered portion 128 of theshell 110 that surrounds narrowing region 118 of exhaust pathway 112.Filter element 190 captures ionized particles that are attracted to thehigh electrical potential of the shell, such as particulate matter orother combustion products contained within the exhaust gases. Remainingexhaust gases are discharged from shell 110 via outlet portion 134.

Non-limiting use-environments for exhaust system 100 include withinvehicle exhaust systems, building exhaust systems, building HVACsystems, building emergency/fire exhaust systems, and exhaust systemsfor electrical power generation to name a few examples. As a propheticexample, exhaust system 100 may eliminate approximately 80% of productsof combustion from the exhaust gases without adding undue flowobstruction or backpressure to the exhaust pathway. Another potentialbenefit of the ionization of exhaust gases provided by exhaust system100 includes the reduction of odors contained in the exhaust gases, forexample, by the production of ozone via the ionization process.

In this example, filter element 190 covers interior surfaces of thetapered portion of the shell and tapers with the tapered portion of theshell. For example, filter element 190 tapers inward toward longitudinalaxis 114 in the first direction 116 along longitudinal axis 114, andforms a generally conical structure. Filter element 190 may have acircular shape when viewed in section along longitudinal axis 114. Inother examples, filter element 190 may have a non-circular shape whenviewed in section (e.g., to conform with a shell having a non-circularshape), such as a non-circular oval shape, polygonal shape, or othersuitable shape. Another view of filter element 190 is depicted in FIG.4. FIG. 1 further depicts an example in which a downstream end of filterelement 190 extends beyond tapered portion 128 and projects into exhaustpathway 112, as indicated at 192. In other examples, filter element 190may conform to interior walls of tapered portion 128 without extendingbeyond tapered portion 128 or without projecting into exhaust pathway112. Filter element 190 may take the form of a paper filter or othersuitable filter type that is disposable or alternatively reusable. Insome examples, filter element 190 may be omitted. If the filter elementis omitted, ionized exhaust gas components that are attracted to theshell may adhere to interior surfaces of the shell and thereby removedfrom the exhaust gases that exit the exhaust system.

FIG. 2 depicts an example of an external view of exhaust system 100 ofFIG. 1. Shell 110 from FIG. 1 may be formed by one or more shellcomponents. In this example, a shell is formed by an inlet shellcomponent 210 and an outlet shell component 212 that join each other atan interface 214 to collectively define exhaust pathway 112. An internalview of interface 214 is depicted in FIG. 1 as including an overlappingregion 136 depicted in FIG. 1, in which outlet shell component 212surrounds and overlaps with inlet shell component 210 within overlappingregion 136. In other examples, shell 110 may be formed by a single shellcomponent, or by three or more shell components.

In this example, inlet shell component 210 includes an inlet portion120, an inlet-side tapered portion 122 that tapers outward away fromlongitudinal axis 114 in the first direction 116 (shown in FIG. 1), anda first intermediate portion 124. Also in this example, outlet shellcomponent 212 includes a second intermediate portion 126 that interfaceswith first intermediate portion 124 at interface 214. Outlet shellcomponent 212 further includes previously described tapered portion 128,and an outlet portion 134. Outlet shell component 212 may optionallyinclude an additional outlet-side tapered portion 132 that furthertapers inward toward longitudinal axis 114 in the first direction 116,and an additional intermediate portion 130 located between taperedportion 128 and outlet-side tapered portion 132. In other examples,intermediate portion 130 and outlet-side tapered portion 132 may beomitted, such that tapered portion 128 joins outlet portion 134, asdepicted in FIG. 3, for example.

FIG. 4 depicts an exploded view of exhaust system 100 of FIG. 1. WithinFIG. 4, first intermediate portion 124 of inlet shell component 210 mayinclude a plurality of keyways 412 (or slots) located along a terminalend of the inlet shell component that accommodate a correspondingplurality of shafts 410 (or other suitable key structures) that projectfrom an interior surface of second intermediate portion 126 of outletshell component 212. FIG. 6 depicts additional aspects of keyways 412and shafts 410 in further detail. Shafts 410 may be inserted intokeyways 412 and inlet shell component 210 may be rotated relative tooutlet shell component 212 to lock or otherwise secure shell component210 to outlet shell component 212. Opening 420 in inlet shell component210 is aligned with opening 422 in outlet shell component 212 whenshafts 410 are fully inserted and rotated into keyways 412. A fastener424 (e.g., a bolt, screw, pin, or other suitable fastener) may beinserted into openings 420 and 422 to inhibit rotation of inlet shellcomponent 210 relative to outlet shell component 212, thereby precludingshafts 410 from exiting keyways 412.

FIG. 4 further depicts insulating support structure 144 including threearms 460, 462, and 464 that are secured to inlet shell component 210.FIGS. 5, 7, and 8 depict additional views of insulating supportstructure 144. Inlet shell component 210 further includes an opening 416through which a fastener 418 (e.g., e.g., a bolt, screw, pin, or othersuitable fastener) may be inserted and engaged with an opening 414 in aterminal end of arm 462 to secure insulating support structure 144 tothe shell. Arm 464 may be secured to inlet shell component 210 in asimilar manner as arm 462. Arm 460 includes an opening 436 that alignswith opening 438 in inlet shell component 210. A deformable fastener 440may be inserted through opening 438 to engage with opening 436 of arm460. A compression cap 442 engages with deformable fastener 440 toprovide a clamping force that secures one or more wires, cables, orother suitable electrical pathways that pass through opening 450. Asshown in further detail in FIGS. 5, 7 and 8, opening 450 passes throughcap 442, deformable fastener 440, inlet shell component 210 (via opening438), and arm 460 (via opening 436), and connects to opening 428 locatedin a hub of insulating support structure 144. Electrical pathway 179(shown in FIG. 1) may pass through opening 450 to be connected withelectrically conductive components of the ionization assembly, such asdiscs 146 and support arm 142.

Support arm 142 may be secured to insulating support structure 144 atopening 428 via an intermediate fastener 426. Opening 428 passes throughthe hub of insulating support structure 144, enabling a fastener 432located on an upstream side of support structure 144 to engage withintermediate fastener 426 through opening 428. A cover 434 may beinserted into opening 428 over fastener 432 on the upstream side ofinsulating support structure 144 to provide a more aerodynamic upstreamsurface.

FIG. 5 depicts insulating support structure 144 and surrounding firstintermediate shell portion 124 in further detail as viewed alonglongitudinal axis 114. Insulating support structure 144 is shown infurther detail including hub 510, which joins arms 460, 462, and 464that radially project from the hub. Arms 460, 462, and 464 are depictedas each including a number of fin structures. Arms 462 and 464 aresecured to first intermediate shell portion 124 by fasteners 418inserted into openings 414 formed at a terminal end of arms 462 and 464.Inlet portion 120 is depicted in FIG. 5 for illustrative purposes, andis located upstream of insulating support structure 144. Opening 450 isdepicted passing through cap 442, deformable fastener 440, arm 460, andjoins with opening 428 formed in hub 510. Arm 460 is secured to firstintermediate shell portion 124 by deformable fastener 440, as depictedin further detail in FIGS. 7 and 8.

FIG. 6 depicts overlapping region 136 of interface 214 between shellcomponents 210 and 212 in further detail, as viewed along longitudinalaxis 114. First intermediate portion 124 of inlet shell component 210 isdepicted within second intermediate portion 126 of outlet shellcomponent 212. Shafts 410 are engaged with keyways 412 in FIG. 6.Fastener 424 passes through opening 422 in first intermediate portion126 and engages with second intermediate portion 124 via opening 420 toinhibit portions 124 and 126 of the shell from rotating and/ordisengaging from each other.

FIG. 7 depicts additional aspects of ionization assembly 140 in anexploded view. Within FIG. 7, an internal view of insulating supportstructure is provided, which reveals internal threads within opening 436that engage with external threads 718 of a lower portion of deformablefastener 440. Deformable fastener 440 further includes an upper portionthat includes external threads 720 that engage internal threads 722 ofcompression cap 442. When compression cap 442 is threaded ontodeformable fastener 440 via threads 720 and 722, internal wall surfacesthat define an interior region 726 of compression cap 442 contactdeformable elements 724 causing the deformable elements to deforminward, thereby providing a clamping force on an object (e.g., a wire,cable, or other electrical pathway) that passes through deformablefastener 440 via opening 450.

Opening 450 joins opening 428 that passes through hub 510. Fastener 432having external threads may be inserted into opening 428 on the upstreamside of support structure 144 where it engages internal threads ofintermediate fastener 426 to retain intermediate fastener within opening428 on the downstream side of the support structure. Cap 434 may beinserted behind fastener 432 to cover opening 428. When fastener 432 isthreaded onto intermediate fastener 426, the fasteners may collectivelyprovide a clamping force upon a narrowed region 714 of opening 428 ofthe support structure. Intermediate fastener 426 further includesinternal threads 711 that accommodate external threads of support arm142. In at least some examples, intermediate fastener 426 includes anopening 716 that aligns with opening 450 when threads 712 are engagedwith threads of fastener 432. Opening 716 may accommodate one or morewires, cables, electrical connectors, or other suitable electricalpathways that pass through opening 450 from outside of the ionizationassembly.

FIG. 8 depicts components of ionization assembly 140 in an assembledconfiguration. In FIG. 8, a wire 812 passing through opening 450 isconnected to a low electrical potential of a voltage source. Wire 812terminates at a conductive element 810 (e.g., an electrical connector)that is sized and shaped for insertion into opening 716 of intermediatefastener 426. In some examples, fastener 432 may extend to or beyondopening 716 and may contact conductive element 810 when threaded intothreads 712 of intermediate fastener 426 to retain or otherwise clampconductive element 810 within opening 716. Additionally oralternatively, deformable elements 724 may clamp onto wire 812 to retainconductive element 810 within opening 716 when cap 442 is threaded ontodeformable fastener 440. Intermediate fastener 426 and fastener 432 maybe electrically conductive to establish an electrical pathway betweenconductive element 810 and support arm 142 upon which the electricallyconductive discs are mounted and supported.

FIGS. 9 and 10 depict an example of an electrically conductive disc 900.Disc 900 is a non-limiting example of any of the previously describedelectrically conductive discs 146 of FIGS. 1 and 4. FIGS. 9 and 10provide an example orientation of disc 900 relative to the samecoordinate system of FIGS. 1 and 4. For example, FIG. 9 depicts a face910 of disc 900 presented orthogonal to the view provided by FIG. 9,which is parallel with the X-coordinate axis and longitudinal axis 114of FIG. 1. FIG. 10 depicts disc 900 in the same orientation as discs 146of FIG. 1.

In this example, disc 900 has a circular shape bounded by outer edge912. Disc 900 has an opening 916 located at a centroid of its circularshaped face 910 to accommodate a support arm, such as previouslydescribed support arm 142. In some examples, a diameter of opening 916may vary among or between each disc of an ionization assembly thatcontains a plurality of electrically conductive discs. In this example,a support arm for supporting the plurality of discs may vary in size(e.g., diameter) and/or shape along its length to define a particularlocation along its length where each disc resides. For example,referring also to FIG. 1, a size (e.g., a diameter) of support arm 142decreases in a step-wise manner between each disc as the support armextends away from insulating support structure 144 and alonglongitudinal axis 114 in the first direction 116. In this example, eachof the plurality of discs 146 has an opening at its centroid foraccommodating support 142, in which the size (e.g., diameter) of eachopening decreases as the size of the disc decreases.

Also in this example, disc 900 tapers toward outer edge 912 as indicatedby tapered region 914 to provide a sharp outer edge or corner that mayimprove ionization of exhaust gas components flowing over or past thedisc. FIG. 10 depicts an example taper angle 1000 for tapered region914. In FIG. 10, taper angle 1000 is measured relative to face 910 ofthe disc. As a non-limiting example, taper angle 1000 may be 28 degrees.As another example, taper angle 1000 may be between 25 degrees and 30degrees. As yet another example, taper angle 1000 may be greater thanzero degrees and less than 30 degrees. As yet another example, taperangle 1000 may be an angle greater than 28 degrees. A taper angle may bethe same for either side of a disc to provide a symmetric configuration,such as depicted in FIG. 10. In other examples, a taper angle on oneside of a disc may differ from a taper angle on an opposite side of thedisc.

The various components described as being electrically conductive may beformed from any suitable material that provides substantial electricalconductivity, including materials that are or include electricallyconductive metals such as copper, steel, aluminum, and iron, to name afew non-limiting examples. Components described as being electricallyinsulating, such as support structure 144 of ionization assembly 140,may be formed from any suitable material that does not providesubstantial electrical conductivity. Where the electrically insulatingmaterial is located within the exhaust pathway that may contain exhaustgases of relatively high temperatures or is otherwise used in hightemperature environments (such as support structure 144 located withinthe exhaust pathway) suitable electrically insulating materials mayinclude ceramic, heat-tolerant polymers, or other heat tolerantelectrical insulators.

The drawings accompanying this disclosure include schematicrepresentations of example geometries and configurations. These drawingsare not necessarily to scale. A non-limiting example of physicalmeasurements for components of exhaust system 100 is provided below.These physical measurements in combination with each other describe anon-limiting example of the relative sizes and shapes of exhaust systemcomponents. These relative sizes and shapes may vary (e.g., by 10%, by20%, or more) from the specific physical measurements described hereinwhile still providing suitable or adequate removal of exhaust gascomponents.

In a non-limiting example, each of discs 146 have a thickness of 1 cmand are spaced 20 cm apart from each other on support structure 142.Disc 150 has a diameter of 75.7 cm and an opening at its centroid of 9cm. Disc 152 has a diameter of 66.2 cm and an opening at its centroid of8 cm. Disc 154 has a diameter of 56.7 cm and an opening at its centroidof 7 cm. Disc 156 has a diameter of 47.2 cm and an opening at itscentroid of 6 cm. Disc 158 has a diameter of 37.7 cm and an opening atits centroid of 5 cm. Disc 150 has a diameter of 28.2 cm and an openingat its centroid of 4 cm. Outlet shell component 212 has a total length,as measured along longitudinal axis 114 of 270 cm. Tapered portion 128has a length of approximately 182.3 cm, and tapers from a diameter of111.6 cm to 42 cm with walls having a taper angle of 11 degrees relativeto longitudinal axis 114. Inlet shell component 210 has a total lengthof 155 cm as measured along longitudinal axis 114 and varies in diameterfrom 68.4 cm to 110 cm. Support structure 144 has a thickness of 40 cmas measured along the longitudinal axis 114, with arms 460, 462, and 464radially projecting from hub 510 at approximately 120 degrees relativeto each other. Filter element 190 has a total length of 178.3 cm asmeasured along the longitudinal axis, and tapers from a diameter of109-110 cm to 41 cm with walls having a taper angle of 11 degreesrelative to longitudinal axis 114.

The various examples disclosed herein include features that may be usedindividually or in any combination. Claimed subject matter is notlimited to the combination of features disclosed by an individualexample, since features that are present in two or more of the disclosedexamples may be used together in other combinations. Accordingly, itshould be understood that the disclosed examples are illustrative andnot restrictive. Variations to the disclosed examples that fall withinthe metes and bounds of the claims or equivalence of such metes andbounds are intended to be embraced by the claims.

1. An exhaust system, comprising: an electrically conductive shelldefining an exhaust pathway, the shell having a tapered portion thattapers inward toward a longitudinal axis of the shell to define anarrowing region of the exhaust pathway that narrows in a firstdirection along the longitudinal axis; an ionization assembly,including: a support arm located within the exhaust pathway andextending into the narrowing region of the exhaust pathway, a pluralityof electrically conductive discs supported by the support arm, with atleast some of the discs located within the narrowing region of theexhaust pathway, the discs spaced apart from each other along thelongitudinal axis, the discs decreasing in size relative to each other,as measured in a plane orthogonal to the longitudinal axis, in the firstdirection along the longitudinal axis; and an electrical subsystem,including: a voltage source having a high electrical potential terminalin electrical communication with the shell, and a low electricalpotential terminal in electrical communication with the discs.
 2. Theexhaust system of claim 1, further comprising: a filter element coveringinterior surfaces of the tapered portion of the shell and tapering withthe tapered portion of the shell.
 3. The exhaust system of claim 1,wherein the ionization assembly further includes an electricallyinsulating support structure located within the exhaust pathway, andsecured to the shell at one or more points; and wherein the support armis supported relative to the shell by the electrically insulatingsupport structure.
 4. The exhaust system of claim 3, wherein theelectrically insulating support structure is secured to shell at leastat three points radially spaced apart from each other about longitudinalaxis.
 5. The exhaust system of claim 3, wherein the support arm projectsfrom the insulating support structure in the first direction along thelongitudinal axis of the exhaust pathway.
 6. The exhaust system of claim5, wherein the support arm is collinear with the longitudinal axis ofthe exhaust pathway.
 7. The exhaust system of claim 6, wherein thesupport arm passes through each of the plurality of electricallyconductive discs at a centroid of a face of each of the discs that isorthogonal to the longitudinal axis.
 8. The exhaust system of claim 1,wherein the plurality of electrically conductive discs includes five ormore electrically conductive discs.
 9. The exhaust system of claim 1,wherein the plurality of electrically conductive discs includes at leastsix electrically conductive discs.
 10. The exhaust system of claim 1,wherein the plurality of electrically conductive discs includes exactlysix electrically conductive discs.
 11. The exhaust system of claim 1,wherein each of the plurality of electrically conductive discs have acircular shaped face that is orthogonal to the longitudinal axis. 12.The exhaust system of claim 1, wherein each of the plurality ofelectrically conductive discs have sharp tapered edges.
 13. The exhaustsystem of claim 1, wherein the electrical subsystem further includes oneor more intermediate switches that enable one or both of the highelectrical potential terminal and/or the low electrical potentialterminal to be electrically disconnected from the shell and/or thediscs.
 14. An ionization assembly for an exhaust system, the ionizationassembly comprising: an electrically insulating support structure havingone or more mounting surfaces for securing the support structure to anelectrically conductive shell defining an exhaust pathway of the exhaustsystem; a support arm secured to the support structure; and a pluralityof electrically conductive discs mounted on the support arm, the discsspaced apart from each other and decreasing in size relative to eachother along the support arm.
 15. The ionization assembly of claim 14,wherein the plurality of electrically conductive discs includes five ormore circular electrically conductive discs.
 16. The ionization assemblyof claim 15, wherein the support arm passes through each of theplurality of electrically conductive discs at a centroid of a face ofeach of the discs that is orthogonal to the support arm.
 17. Theionization assembly of claim 16, wherein each of the plurality ofelectrically conductive discs have sharp tapered edges.
 18. Theionization assembly of claim 14, wherein the electrically insulatingsupport structure includes three arms radially spaced about a hub inwhich the one or more mounting surfaces include a mounting surfacelocated at a terminal end of each arm.
 19. An exhaust system,comprising: an electrically conductive shell defining an exhaustpathway, the shell having a tapered portion that tapers inward toward alongitudinal axis of the shell to define a narrowing region of theexhaust pathway that narrows in a first direction along the longitudinalaxis; an ionization assembly, including: an electrically insulatingsupport structure located within the exhaust pathway, and secured to theshell at one or more points, a support arm located within the exhaustpathway and extending into the narrowing region of the exhaust pathway,the support arm is supported relative to the shell by the electricallyinsulating support structure. a plurality of electrically conductivediscs mounted on and supported by the support arm, with at least some ofthe discs located within the narrowing region of the exhaust pathway,the discs spaced apart from each other along the longitudinal axis, thediscs decreasing in size relative to each other, as measured in a planeorthogonal to the longitudinal axis, in the first direction along thelongitudinal axis; and a filter element covering interior surfaces ofthe tapered portion of the shell and tapering with the tapered portionof the shell.
 20. The exhaust system of claim 19, further comprising: anelectrical subsystem, including: a voltage source having a highelectrical potential terminal in electrical communication with theshell, and a low electrical potential terminal in electricalcommunication with the discs.